Biomedical subjects

G Mancia

Publications and source records attributed to G Mancia.

At least 361 records · Page 20Linked to original sources

PubMed1992

Twenty-four-hour blood pressure and antihypertensive treatment.

Normal values for 24-hour blood pressure (BP) have not been well characterized. However, it is believed that the maintenance of normal blood pressure control is a desirable feature of an antihypertensive agent. This is particularly important with respect to the drug's ability to (1) maintain circadian variation, albeit from a lower baseline, (2) lower BP throughout the 24 hours, (3) avoid the development of postural hypotension, (4) avoid decreases in BP sufficient to precipitate an ischemic event, (5) and to reduce BP variability toward the normal BP limits.

Antihypertensive Agents↗

PubMed1992

The neck chamber technique.

Since the first description of the neck chamber technique for stimulating carotid baroreceptors by Ernsting and Parry in 1957, a number of different neck collars have been realized, among which the simplified version devised by Eckberg and coworkers in 1975 and the neck chamber described by Ludbrook and coworkers in our Institute in 1977. At variance with Eckberg's type, the "Milan neck chamber" completely surrounds the neck and allows the application of both positive and negative pressures to the neck by means of a system of double rubber valves that prevents air leakage from the chamber. The main advantage of this technique, as compared to infusion of vasoactive drugs, is the possibility it offers to study baroreflex control not only of heart rate, but also of peripheral resistance and blood pressure through neck chamber induced changes in carotid transmural pressure. In recent years a systematic evaluation of the neck chamber technique has allowed to clarify the following issues: 1) application of positive pressure to the neck, although increasing internal jugular venous pressure and thereby reducing the pressure gradient from the arterial versus the venous side of head circulation, does not reduce cerebral blood flow; 2) changes in pressure within the neck chamber do not seem to reduce blood flow to the carotid bodies, at least to a degree which might lead to chemoreceptor stimulation; 3) there is a linear relation between changes in neck chamber pressure and changes in tissue pressure adjacent to the carotid sinus. The transmission of pressure to pericarotid tissues is complex, however.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Pressure↗

PubMed1992

Variability in arterial diameter and compliance: compliance modulation reserve.

BACKGROUND: Some antihypertensive drugs are known to increase arterial compliance in hypertensives; how far compliance can be increased is unknown. DESIGN: We studied eight mildly hypertensive patients to determine how far radial artery compliance can be acutely increased, i.e. the extent of the compliance modulation reserve. METHODS: We evaluated radial artery compliance by a new technique, assessing it throughout the cardiac cycle before and after the intra-arterial infusion of a vasodilator agent (papaverine). RESULTS: Before papaverine, compliance decreased progressively through diastolic to systolic blood pressure values. This was the case also during the papaverine infusion. However, over the full systolo-diastolic pressure range, compliance was increased by about 40% with papaverine. CONCLUSIONS: In hypertensive subjects radial artery compliance can be markedly increased on a acute basis, indicating that those antihypertensive drugs that improve compliance have a considerable reserve to act upon.

Adult↗

PubMed1992

Changes in arterial compliance induced by physical training in hammer-throwers.

OBJECTIVE: Physical training induces multiple changes in the cardiovascular system which allow an increased performance along with increased oxygen consumption. The present study was designed to investigate whether the changes include an increase in arterial compliance. METHODS AND DESIGN: In six normotensive right-handed hammer-throwers (aged 21.3 +/- 1.8 years, mean +/- SE) we measured radial artery diameter continuously via a new non-invasive echo-tracking device, and beat-to-beat blood pressure. Arterial compliance was calculated by an arctangent model. In each subject measurements were made from both the left and the right arm. The data were compared with those obtained in six age-matched normotensive controls. RESULTS: Compared to the controls, the hammer-throwers had similar blood pressure, a lower heart rate and plasma norepinephrine and a higher left ventricular mass index and radial artery diameter. In the athletes, right radial artery compliance was significantly greater than either right or left radial artery compliance in the sedentary subjects (+61 and 63%, P < 0.05). It was also significantly greater than contralateral radial artery compliance (+53 +/- 8%, P < 0.05). CONCLUSIONS: Physical training is accompanied by an increase in arterial compliance. In our hammer-throwers this increase was mainly evident in the more highly trained arm, suggesting that local mechanisms are involved in this phenomenon.

Adult↗

PubMed1992

[Efficacy and tolerability of nicardipine retard and captopril in hypertension in the aged. Results of a multicenter study].

The efficacy and tolerability of nicardipine retard and captopril were assessed in 174 over-60-year-olds suffering from slight or moderate essential hypertension. After 2-3 weeks of wash out the patients were randomly assigned to calcium antagonist (40 mg twice a day) or ace-inhibitor (25 mg twice a day) treatment which continued for 180 days. Monotherapy was combined with hydrochlorothiazide (12.5 mg/day) after 2 months in the event of an unsatisfactory reduction of arterial pressure in relation to basal values. Systolic and diastolic blood pressure was measured (1st and 5th Korotkoff's tone) at monthly intervals while lying and standing; heart rate was also measured using a palpatory method. Both nicardipine retard (no. 86) and captopril (no. 88) caused a significant reduction of clino- and orthostatic systolic and diastolic arterial pressure during the first two months of treatment. Respectively 70% and 51% of patients responded to treatment and the blood pressure reductions achieved using monotherapy remained unchanged during the course of the study. The association of hydrochlorothiazide resulted in a significant decrease in arterial pressure in non-responders, an effect which was observed with both nicardipine retard and captopril. No significant variation in heart rate was recorded between the two groups. Twenty-one patients in the nicardipine retard group and 16 in the captopril group suffered from slight to moderate side effects. Six patients dropped out of the nicardipine retard group and 15 patients out of the captopril group, an event for which side-effects were responsible in 1 and 3 cases respectively. In conclusion, nicardipine retard and captopril represent an efficacious form of treatment for geriatric hypertension and possess a satisfactory level of tolerability.

Aged↗

PubMed1992

Twenty-four hour blood pressure variability: clinical implications.

Ambulatory blood pressure monitoring techniques have allowed quantification of blood pressure variations occurring over a 24 hour time. The evaluation of these phenomena has not only allowed us to investigate the mechanisms responsible for cardiovascular regulation, but it has also provided information of clinical value. In particular there is evidence that blood pressure variations are significantly related to cardiovascular complications of hypertension. Progress in technology may allow us to extend these observations by means of non-invasive continuous blood pressure recordings to all those conditions where intra-arterial methods are not allowed.

Blood Pressure↗

PubMed1992

[The Study Group of Quinapril in Arterial Hypertension. The Steering Committee].

The efficacy and safety of the treatment of arterial hypertension with the ACE-inhibitor quinapril, were evaluated in a multicentre study conducted in Italy. The study, lasting 14 weeks, after a preliminary wash-out period, allowed response-based titration of quinapril dose from 10 mg to 40 mg once a day, with provision to combine additional hydrochlorothiazide (12.5 to 25 mg), in case of persistently high diastolic pressure levels. The efficacy sample included 1267 patients: at therapy week 14, 78.6% of patients were treated with quinapril alone. Global response rate (intent-to-treat) was 83.3%, with a mean reduction of diastolic pressure of 15.8 mmHg (95% confidence interval from 15.5 to 16.2 mmHg). 91 patients reported 126 associated adverse events (7.0%); the most frequently reported event was cough (2.7%). First-dose hypotension was rarely reported (1.3%), even in elderly and diabetic patients.

Angiotensin-Converting Enzyme Inhibitors↗

PubMed1991

Reflex control of circulation in the elderly.

Baroreceptor control of heart rate is markedly reduced in elderly subjects. However, the effects of aging on baroreceptor control of blood pressure and on the vascular and neurohumoral influences of volume cardiopulmonary receptors are unknown. In this paper we report evidence that in both conscious rats and humans aging is associated with a fall in the baroreceptor ability to rapidly cause blood pressure changes, but that the more long-term carotid baroreceptor control of blood pressure remains similar to that observed in younger individuals. Early and late cardiopulmonary receptor modulation of vascular resistance is impaired by aging, which also reduces the influence of this reflex on renin secretion. These dynamic and steady-state alterations in reflex cardiovascular control account for several hemodynamic abnormalities of the advanced age.

Aged↗

PubMed1991

Assessment of sympathetic cardiovascular influences in man: haemodynamic and humoral markers versus microneurography.

Evaluation of sympathetic cardiovascular influences has important physiological, pathophysiological and clinical implications. This paper reviews some of the methods employed to measure these influences in man, along with their advantages and disadvantages. The most useful methods appear to be the measurement of plasma noradrenaline (particularly when modified to calculate spillover rate of noradrenaline) and direct recording of sympathetic nerve traffic. With the former, despite the technological advances in measurement, certain methodological problems remain, such as the separation of noradrenaline secretion from clearance. With the latter technique peripheral muscle and skin sympathetic activity can be measured separately but the question of regional vascular variability has still to be resolved. A combination of these two methods may represent the ideal approach. This review considers the complex problems associated with attempts to precisely quantify sympathetic cardiovascular influences in man.

Animals↗

PubMed1991

Use of intravenous digital subtraction ventriculography in the evaluation of left ventricle volumes and ejection fraction.

Although intravenous digital subtraction ventriculography (IDSV) is increasingly used to estimate end-diastolic left ventricular volume (EDV), end-systolic left ventricular volume (ESV) and left ventricular ejection fraction (EF), its ability to reproduce the precise estimates provided by left ventricle cineangiography (LVCA) and its role in clinical cardiology have not been unequivocally established. In 32 patients subjected to cardiac catheterization for a variety of cardiac disorders and a normal or reduced left ventricular function the EDV, ESV and EF provided by a 30 degrees right anterior oblique LVCA were compared with those provided by a 30 degrees right anterior oblique IDSV. The mean EDV, ESV and EF obtained by IDSV in the 32 patients were superimposable on those obtained by LVCA. The individual EDV, ESV and EF values provided by the two methods were all related in a close linear fashion. For EF the correlation coefficient was 0.98 and the 90% confidence interval of the mean difference between the two series of values was +/- 6.1%, i.e. +/- 10% error compared to the mean EF provided by LVCA. Thus IDSV is a reliable and not too invasive method for estimating left ventricle volumes and ejection fraction. It might provide serial estimations with a better assessment of the evolution of a patient's disease and the effect of treatment.

Adult↗

PubMed1991

Reproducibility of non-invasive and intra-arterial blood pressure monitoring: implications for studies on antihypertensive treatment.

Ambulatory blood pressure has been shown to be more reproducible than office blood pressure and thus to be more suited for studying the efficacy of antihypertensive drugs. In 34 untreated essential hypertensive subjects, we measured office and 24-h non-invasive or intra-arterial blood pressure twice over a 4-week interval; 24-h intra-arterial blood pressure was obtained by the Oxford method whereas 24-h non-invasive blood pressure was obtained by the automatic SpaceLabs 5300 device, with a 10 min (daytime) or 20 min (night-time) interval between measurements. The standard deviation of the mean difference (s.d.d.) between blood pressures obtained in each recording was taken as the reciprocal of blood pressure reproducibility. The s.d.d. was highest for office blood pressure and for single blood pressure readings taken from 24-h non-invasive recordings. The s.d.d. fell when the two 24-h average non-invasive blood pressures were considered. The fall was progressively greater as the number of ambulatory readings on which the average was calculated increased from two to 24, no further fall being observed when more than 24 values were considered. The maximal reduction in s.d.d. was 59% (systolic) and 42% (diastolic) as compared with the office s.d.d. The two 24-h mean values obtained by the intra-arterial approach were slightly more closely correlated than those obtained non-invasively. However, at comparable sampling rates, the s.d.d. was not substantially lower with 24-h intra-arterial blood pressure and including in the calculation the average of the thousand readings provided by this approach did not cause any further improvement.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1991

Effect of placebo on 24-h non-invasive ambulatory blood pressure.

Twenty-four-hour mean ambulatory blood pressure has been shown to be devoid of a placebo effect. However, whether this is the case for different periods within the 24 h has not been established. In 27 essential hypertensive outpatients, blood pressure was measured in the doctor's office and by 24-h ambulatory blood pressure monitoring after a 3-week wash-out period from antihypertensive treatment (Control) and following 4 weeks of placebo administration. Office systolic and diastolic blood pressures were reduced by placebo (-9.6 +/- 2.6 and -3.1 +/- 1.7 mmHg, P less than 0.01, respectively), whereas 24-h mean blood pressure values did not show any significant change. This was not the case for all 24-h subperiods, however, because during the initial 8h, systolic and diastolic blood pressures were slightly (-4.1 +/- 9.2 and -2.5 +/- 6.4 mmHg) but significantly (P less than 0.05) lower during placebo than during control. Similar findings were obtained in 14 additional essential hypertensive patients in whom neither placebo nor any other treatment was employed between the two office and 24-h blood pressure measurements. Thus, placebo treatment is associated with a blood pressure reduction in the initial portion of the ambulatory blood pressure profile, probably because of an attenuation of an initial transient alerting response to the procedure. Although so small as to leave the 24-h blood pressure mean unaffected, this may lead to some overestimation of the antihypertensive effect of treatment during an appreciable portion of the circadian blood pressure tracing.

Adult↗

PubMed1991

Differential effects of aging on the heart rate and blood pressure influences of arterial baroreceptors in awake rats.

The effect of aging on arterial baroreceptor control of heart rate and blood pressure was evaluated in unanesthetized normotensive rats aged 5-6 (young), 12-16 (adult) and 75-90 (old) weeks. Each rat was chronically implanted with arterial and venous femoral catheters and with bilateral balloon-in-cuff occluders around the common carotid arteries. Baroreceptor control of heart rate was assessed by the bradycardic and tachycardic response to intravenous boluses of phenylephrine and nitroprusside, respectively. Carotid baroreceptor control of blood pressure was assessed by a 12-s bilateral common carotid occlusion (CCO). All baroreflex responses were similar in young and adult rats. Compared with the young group, old rats showed a marked reduction of the bradycardic and tachycardic baroreflex response (-42% and -46%, respectively, P less than 0.05). The initial pressor responses to CCO were also impaired in the old animals (3 s: -63%, 6 s: -54%; both P less than 0.01), whereas the peak pressor response (9 and 12 s) was virtually identical in the young and old groups. The preservation of the peak pressor response to CCO in old rats was independent of chemoreceptor activation, aortic baroreceptors or cerebral ischemia. Thus, aging impairs baroreceptor control of heart rate but alters baroreceptor control of blood pressure, as assessed by the pressor response to CCO, only in its fast-developing component, leaving its longer-term component unaffected.

Aging↗

PubMed1991

Left ventricular hypertrophy and the 'cardiogenic reflex' in man.

In man, cardiac receptors exert a continuous restraint on sympathetic activity. Reflexes originating from the heart also restrain renin and vasopressin secretion, thereby being involved both in blood pressure and in blood volume homeostasis. We have shown that these reflexes are markedly depressed in subjects with left ventricular hypertrophy (LVH) due to hypertension and that this is also the case when, in normotensive subjects, LVH is caused by prolonged physical training. In both instances, the cardiogenic reflex impairment is associated with derangement of blood pressure homeostasis. Either spontaneous regression of LVH by physical training cessation or antihypertensive treatment is followed by a marked improvement of the cardiogenic reflex. Thus, LVH also affects the 'afferent' function of the heart. 'Physiological', as well as pathological, hypertrophy has a similar adverse effect. This effect is reversible, however, and the reflex function can be restored by regression of hypertrophy.

Autonomic Nervous System↗

PubMed1991

24-hour blood pressure monitoring in hypertension.

It has been recognized for some time that blood pressure is highly variable over a 24-h period. A number of studies have demonstrated that the extent and severity of target-organ damage associated with hypertension can be correlated more closely with blood pressure values monitored continuously for 24 h than with individual values recorded sphygmomanometrically. A great deal of interest is focused on whether absolute values of diastolic or systolic blood pressure, values during the day or night, or the rate of change of blood pressure such as the rapid increase that occurs in the early morning are more or less important factors contributing to the mortality and morbidity associated with hypertension. Work from our own unit provides evidence of the importance of two features in the variability of blood pressure. Blood pressure decreases during the night, but remains higher in hypertensive patients than in normotensive subjects. The mean nighttime blood pressure was shown to correlate with hypertension-related target-organ damage almost as closely as the mean daytime blood pressure. Using 24-h blood pressure monitoring, we have shown that the higher the mean 24-h blood pressure, the greater the extent and severity of target-organ involvement. In addition, for patients with comparable mean 24-h blood pressure values, larger degrees of blood pressure variability throughout the monitoring period were associated with more target-organ damage. Taking the available evidence into account, it is probably important that treatments used for hypertension should provide control of blood pressure for a full 24-h period confirmed by ambulatory blood pressure monitoring.

Antihypertensive Agents↗

PubMed1991

Alterations in cardiac parasympathetic function in aged rats.

Aging impairs sympathetic and parasympathetic cardiac control. Although the reduced sympathetic responses are known to depend on an age-related cardiac beta-adrenoceptor dysfunction, the hypothesis of a parallel cardiac muscarinic receptor dysfunction underlying the reduced parasympathetic responses has never been tested. We therefore measured the bradycardic responses to graded electrical stimulations of the right efferent vagus and to graded bolus intravenous injections of acetylcholine in anesthetized, vagotomized rats of young (16 wk) and old (103 wk) age. Unexpectedly, the bradycardia was markedly larger (greater than 2-fold) in old than in young rats with both the electrical and the pharmacological stimulus. This indicates that at variance with its effects on beta-adrenergic receptor responsiveness, aging not only fails to impair but actually enhances cardiac muscarinic receptor responsiveness. It also suggests the more general conclusion that aging has complex and diversified effects rather than simply and uniformly depressing biological functions.

Acetylcholine↗

PubMed1991

Role of sinoaortic afferents in modulating BP and pulse-interval spectral characteristics in unanesthetized cats.

Sinoaortic denervation (SAD) is accompanied by an increase in blood pressure (BP) and a reduction in pulse-interval (PI) variance. Little is known, however, about the effect of SAD on the complex BP and PI variability pattern, which is identified by spectral analysis. In nine unanesthetized cats in which intra-arterial BP was monitored before and 7-10 days after SAD, spectral powers (estimated by fast Fourier transform) were calculated for the low frequency (LF, 0.025-0.07 Hz), midfrequency (MF, 0.07-0.14 Hz), and high frequency (HF, 0.14-0.60 Hz) band. The very low frequency (VLF) BP and PI components (VLF less than 0.025 Hz) were also estimated. SAD increased systolic BP variance and decreased PI variance. The reduction of PI variance was paralleled by significant and marked reductions in all PI powers including the VLF components. In contrast, the increase in systolic BP variance was accompanied by a marked increase in LF power, a decrease in MF power, and no change in HF power. The VLF BP components increased after SAD for frequencies between 0.025 and 0.0012 Hz, whereas a sudden marked reduction was observed below 0.0012 Hz. Similar results were obtained for diastolic BP powers. Thus the reduction in PI variance induced by SAD is paralleled by a reduction in all PI fluctuations identified by spectral analysis. This is not the case for the SAD-related increase in BP variance, which is accompanied by an increase, no change, or even a reduction in the different BP spectral components.(ABSTRACT TRUNCATED AT 250 WORDS)

Afferent Pathways↗

PubMed1991

Methodological problems in evaluation of cardiovascular effects of stress in humans.

Cardiovascular effects of stress in humans are often assessed by application of physical or emotional stimuli in a laboratory environment. Although this method provides important information, these procedures have several limitations. First, blood pressure and heart rate responses to laboratory stressors are characterized by a limited within-subject reproducibility. Second, there is poor correlation between blood pressure and heart rate responses to different stressors, which implies that individual reaction to stress may be estimated differently according to the test used. Finally, these responses bear only a limited relation to 24-hour or daytime blood pressure variability, that is, they reflect to only a limited extent the tendency of blood pressure to vary during daily activities. If assessed by techniques that allow blood pressure to be continuously recorded for 24 hours in ambulatory subjects, blood pressure variability represents a possible approach to observation of cardiovascular reactivity away from an artificial laboratory environment. However, whether blood pressure variability should be expressed as a percentage or in absolute values is controversial. Furthermore, although naturally occurring stress may markedly increase blood pressure, 24-hour blood pressure variations also depend on factors that are not related to emotional stimuli. Thus, the study of cardiovascular responses to stress in humans encounters several problems, regardless of the method used.

Blood Pressure↗